Airbags have been credited for saving lives by damping impact of a motor vehicle crash on a vehicle occupant. Not only frontal impact airbags are in use, but also side impact airbags, such as side curtain airbags expanding from the roof line of a vehicle or airbags arranged in a center console or armrest between two car seats. After the gas generator is triggered, the airbag unfolds and provides energy absorption for the seat occupant. An airbag arranged in an armrest pushes itself between the seats and between seat occupants sitting next to each other. Another known airbag design provides an airbag in the vicinity of the center tunnel of the vehicle that inflates above the heads of the vehicle occupants to protect the occupants in the event of a vehicle rollover or of an “off-side” impact.
Airbags are designed to provide a synergetic effect with seat belts that restrain seat occupants in a defined position. At least the front seats of a passenger vehicle and increasingly also the rear seats are provided with three-point seatbelts comprising a lap belt and a shoulder harness extending diagonally across a seat occupant's chest. The shoulder harness limits the forward movement of a seat occupant's upper body in the event of a frontal impact.
In contrast, aircraft passenger seats are usually only equipped with a two-point seatbelt, which is a lap belt without shoulder harness. Two-point seatbelts are more comfortable to wear than three-point seatbelts that limit the range of movement of a passenger's upper body. Thus, passengers may be less likely to keep three-point seatbelts fastened for the duration of a flight. Absent a shoulder harness, in the event of a high deceleration of an aircraft, for instance during an emergency landing or a collision, the torso of a passenger is catapulted forward. This constitutes a potentially dangerous situation, where a forward excursion may result in high head accelerations and possibly head injuries from a seat back of a seat located in front of the seat occupant.
Airbags of current designs pose packaging challenges, based in part on the assumption that a large inflated volume is needed in order to provide the airbag with the sufficient energy absorption during a crash due to the force of the occupant impact. However, problems have been noted to occur with airbags of current design in that they can often be difficult to install in vehicles such as small or compact models where space in the passenger compartment is at a premium.
Moreover, such large and bulky airbags often require complex gas generator units in order to guarantee that the airbag will promptly and properly inflate during a crash. These large and bulky gas generators create additional problems because not only do they further increase the size and complexity of the airbag system, but are often also very expensive. More importantly, multiple and complex gas generators can be very difficult to assemble, install, or repair.
In an airplane with possibly hundreds of seats, large gas generators provided for every seat significantly increase the cost and weight of a passive safety system.